Synthesis of hydrolytically and oxidation‐responsive networks using thiol‐ene “click” chemistry with pentaerythritol tetrakis(3‐mercaptopropionate) and tri/tetra‐acrylates

Thiol‐ene click reactions of pentaerythritol tetrakis(3‐mercaptopropionate) with pentaerythritol tetraacrylate and trimethylolpropane triacrylate were used to prepare polymeric degradable networks. The structure and properties of these networks were studied using Fourier‐transform infrared and Raman spectroscopy, thermal gravimetric analysis and scanning electron microscopy. Degradation of these materials was evaluated in different media including phosphate buffer with and without esterase as well as in oxidative environment with hydrogen peroxide. Exposure of the samples to these media results in their degradation. Slow hydrolytic degradation was observed in phosphate buffer and it was not accelerated by the presence of an enzyme. Faster degradation is observed in solutions of hydrogen peroxide. The mechanisms of this degradation are discussed

Chitosan/Poly(2-ethyl-2-oxazoline) films with ciprofloxacin for application in vaginal drug delivery

Chitosan (CHI) and chitosan/poly(2-ethyl-2-oxazoline) (CHI/POZ)-based films were prepared by casting from aqueous solutions of polymer blends with different compositions. Ciprofloxacin was used as a model drug in these formulations. The weight, thickness, folding endurance and transparency of blend films were measured and characterised. All films had a uniform thickness (0.06 ± 0.01 mm) and exhibited sufficient flexibility. The surface pHs of films ranged from 3.76 ± 0.49 to 4.14 ± 0.32, which is within the pH range suitable for vaginal applications. The cumulative release of the drug from the films in experiments in vitro was found to be 42 ± 2% and 56 ± 1% for pure CHI and CHI/POZ (40:60) films, respectively. Drug-free chitosan/poly(2-ethyl-2-oxazoline) films showed weak antimicrobial activity against Escherichia coli. Drug-loaded CHI and CHI/POZ films showed good antimicrobial properties against both Gram-positive Staphylococcus aureus and Gram-negative bacteria Escherichia coli. Mucoadhesive properties of these films with respect to freshly excised sheep vaginal mucosa were evaluated using a tensile method. It was established that all films were mucoadhesive, but an increase in POZ content in the blend resulted in a gradual reduction of their ability to stick to vaginal mucosa. These films could potentially find applications in vaginal drug delivery

Chitosan/poly(2-ethyl-2-oxazoline) films for ocular drug delivery: Formulation, miscibility, in vitro and in vivo studies

Polymeric films were prepared based on chitosan and its blends with poly(2-ethyl-2-oxazoline) by casting from aqueous solutions. These materials were characterised using a number of physicochemical techniques, including Fourier-transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, wide angle x-ray diffraction, tensile testing and scanning electron microscopy. All these studies indicate that there is a weak intermacromolecular hydrogen bonding between these polymers, which facilitates their complete miscibility in solid state. These films were formulated with sodium fluorescein as a model drug and were evaluated for their potential application in ocular drug delivery both in vitro and in vivo. It was established that the films are biocompatible and mucoadhesive; they are capable of providing a sustained drug release when administered topically on the cornea

Advances in antimicrobial polymeric iodophors

Despite centuries of research on this chemical element, the ability of iodine to form complexes with water-soluble polymers and various other molecules remains a topic of great interest. The fascination with iodine and iodophors arises from their remarkable antimicrobial properties against a wide range of pathogens. This review encompasses historical information on iodine and iodophors, showcases existing iodine-containing products available in the market, explores the diverse physicochemical methods employed to study polymer-iodine complexes, and assesses recently published studies on iodophors. Recent advances in this field include the use of new experimental techniques to get new insights into the mechanisms of complexation and structure of these complexes; preparation of iodophors using novel polymers, nano- and micro-particles; and fabrication of antimicrobial surfaces capable of slow iodine release

Thiol-ene “click reactions” as a promising approach to polymer materials

This review is devoted to relatively new and promising approach to the synthesis of novel organic compounds and polymer materials, based on the “click chemistry” concept. Several types of the “click reactions” (cycloaddition, nucleophilic ring opening, non-aldol carbonyl chemistry, and addition to multiple carbon-carbon bonds) have been described, and the relevant examples have been provided. The “thiol-ene” reactions based on the addition of thiol to unsaturated functional groups of organic molecules have been mostly considered in this review, including their conditions and mechanisms. Diverse and wide range of applications of the thiol-ene “click chemistry” has been demonstrated, including the preparation of biocompatible materials and materials for culture and encapsulation of cells; the synthesis of block copolymers; the development of degradable materials as well as novel homogeneous and hybrid network structures; chromatography, glycopolymer synthesis, immobilization of proteins, stabilization/functionalization of capsules and multilayer systems, functionalized micro- and nanogels, nanomedicine, and development of antitumor drugs

Polymeric iodophors with poly(2-ethyl-2-oxazoline) and poly(N-vinylpyrrolidone): optical, hydrodynamic, thermodynamic, and antimicrobial properties

Formation of iodophors by interactions of poly(2-ethyl-2-oxazoline) and poly(N-vinylpyrrolidone) with molecular iodine dissolved in aqueous solutions with addition of potassium iodide and ethanol has been studied using a range of physicochemical techniques including UV-Vis spectroscopy, viscometry, dynamic light scattering, isothermal titration calorimetry and partitioning through semi-permeable membrane. It was established that poly(2-ethyl-2-oxazoline) exhibits greater ability to bind iodine compared to poly(N-vinylpyrrolidone). Despite the difference in the binding ability of these two polymers, their iodophors exhibited similar antimicrobial properties

Thiolated mucoadhesive and PEGylated nonmucoadhesive organosilica nanoparticles from 3-Mercaptopropyltrimethoxysilane

A novel approach has been developed to synthesize thiolated sub-100 nm organosilica nanoparticles from 3-mercaptopropyltrimethoxysilane (MPTS) through its self-condensation in dimethylsulfoxide in contact with atmospheric oxygen. The formation of MPTS nanoparticles proceeds through the condensation of methoxysilane groups and simultaneous disulfide bridging caused by partial oxidation of thiol groups. These nanoparticles showed excellent colloidal stability in dilute aqueous dispersions but underwent further self-assembly into chains and necklaces at higher concentrations. They exhibited very good ability to adhere to ocular mucosal surfaces, which can find applications in drug delivery. The thiolated nanoparticles could also be easily modified through PEGylation resulting in a loss of their mucoadhesive properties

Hydrogen-bonding-driven self-assembly of PEGylated organosilica nanoparticles with poly(acrylic acid) in aqueous solutions and in layer-by-layer deposition at solid surfaces

PEGylated organosilica nanoparticles have been synthesized through self-condensation of (3-mercaptopropyl)trimethoxysilane in dimethyl sulfoxide into thiolated nanoparticles with their subsequent reaction with methoxypoly(ethylene glycol) maleimide. The PEGylated nanoparticles showed excellent colloidal stability over a wide range of pH in contrast to the parent thiolated nanoparticles, which have a tendency to aggregate irreversibly under acidic conditions (pH < 3.0). Due to the presence of a poly(ethylene glycol)-based corona, the PEGylated nanoparticles are capable of forming hydrogen-bonded interpolymer complexes with poly(acrylic acid) in aqueous solutions under acidic conditions, resulting in larger aggregates. The use of hydrogen-bonding interactions allows more efficient attachment of the nanoparticles to surfaces. The alternating deposition of PEGylated nanoparticles and poly(acrylic acid) on silicon wafer surfaces in a layer-by-layer fashion leads to multilayered coatings. The self-assembly of PEGylated nanoparticles with poly(acrylic acid) in aqueous solutions and at solid surfaces was compared to the behavior of linear poly(ethylene glycol). The nanoparticle system creates thicker layers than the poly(ethylene glycol), and a thicker layer is obtained on a poly(acrylic acid) surface than on a silica surface, because of the effects of hydrogen bonding. Some implications of these hydrogen-bonding-driven interactions between PEGylated nanoparticles and poly(acrylic acid) for pharmaceutical formulations are discussed